Amateur photographs reveal population history of a colonial seabird Jonas Hentati-Sundberg, Olof Olsson  Current Biology  Volume 26, Issue 6, Pages R226-R228 (March 2016) DOI: 10.1016/j.cub.2016.02.007 Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 1 Seabird numbers revealed through photographs. (A) Examples of photographs showing the studied sub-colony of common guillemots at Stora Karlsö. (B) Reconstructed trend for this sub-colony 1918–2015 based on photographs. This sub-colony today constitutes about 15% of the entire Stora Karlsö colony. We divided the sub-colony into 65 sub-areas, distributed in four main areas (indicated as a–d in the photograph from 2015), in which we manually counted birds that were considered incubating or brooding. Because population numbers vary over seasons, we selected only photographs for which we either knew that they were taken between May 1st and July 10th (the peak breeding season) or when we judged that the date of the photograph was within this range based on the vegetation seen on the photographs. For years when we only had photographs on parts of the sub-colony, we made linear interpolation of the natural logarithm of the number of breeding pairs in the missing sub-areas (the log transformation represents an assumption of exponential growth or decline of number of pairs). The interpolation was made using all photographs available, but data reported here include only years where at least 50% of the sub-areas were counted. See Supplemental Experimental Procedures and Table S1 for details. Photos in this figure: 1918 Paul Rosenius (Vänersborgs Museum collection), 1950 Gösta Håkansson (Gotlands Museum collection), 1975 Lars-Erik Norbäck, 2015 Aron Hejdström. Current Biology 2016 26, R226-R228DOI: (10.1016/j.cub.2016.02.007) Copyright © 2016 Elsevier Ltd Terms and Conditions